The present invention relates to a technique for constructing an airbag cover to be installed for a passenger seat of a vehicle.
In the following Patent Document 1(Japanese Unexamined Patent Application Publication No. 2004-001635) for example, an example of a conventional passenger airbag device is disclosed. In this passenger airbag device, there is provided a tear line in the airbag cover for tearing the airbag cover covering an passenger airbag, and the airbag cover is configured so as to be torn along the tear line to allow an opening to be deployed upon occurrence of a vehicle collision, and to allow the passenger airbag to expand to the outside of the airbag cover. In addition, in an airbag cover of this kind, it is common that a top portion of the airbag cover and a joint portion located at a backside of the top portion are joined by means of a vibration welding, using the welding ribs vertically disposed therebetween.
By the way, in an airbag device of this kind, the opening of an airbag cover is configured so as to be deployed toward the side of an occupant as being pushed by an expanding airbag, and therefore a pushing load from the airbag concentrates onto the opening or a particular area therearound, compared to other portions of the airbag cover. For this reason, it is required to secure the strength of the airbag cover in said area.
Accordingly, the present invention has been made in view of the above problem in an airbag cover provided for a passenger seat of a vehicle. The object of the invention is to provide a technique effective to enhance the joint strength of the welding in a particular area between a top portion constituting the opening and a backside of the top portion through a plurality of welding ribs thereby securing the strength of the airbag cover in the particular area.
Further objects and advantages of the invention will be apparent from the following description of the invention.